--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/CacheTimeCheck.inc.php	Sun Jan 22 19:22:00 2023 +0100
@@ -0,0 +1,86 @@
+<?php
+$baseDir = dirname(__FILE__);
+
+include_once 'common-functions.inc.php';
+include_once 'FileCacheSet.inc.php';
+$cache = ScriptIncludeCache::instance(__FILE__);
+$cache->cache_time("${baseDir}/FileCacheSet.inc.php");
+
+function toGMTime($time) {
+  return gmdate('D, d M Y H:i:s', $time) . ' GMT';
+}
+
+/**
+ * Checks if a HTTP_IF_MODIFIED_SINCE header is set, if this file is
+ * newer, set a Last-Modified header, otherwise abort with an 304
+ * status code
+ */
+function CheckHttpModified($cache)
+{
+  if (DEBUG_LEVEL >= VERBOSITY_DEBUG)
+    var_dump($_SERVER);
+
+  $gmdate_mod = toGMTime($cache->getNewest());
+
+  if (array_key_exists('REDIRECT_URL', $_SERVER) && $_SERVER['REDIRECT_URL'] == '/sitemap.xml') {
+    //print_r($gmdate_mod);
+  }
+
+  foreach($cache->cacheControl() as $header => $value) {
+    header ("${header}: ${value}");
+  }
+  if(array_key_exists('HTTP_IF_MODIFIED_SINCE', $_SERVER)) {
+    $HTTP_IF_MODIFIED_SINCE = $_SERVER['HTTP_IF_MODIFIED_SINCE'];
+    $if_modified_since = preg_replace('/;.*$/', '', $HTTP_IF_MODIFIED_SINCE);
+
+    if (strtotime($if_modified_since) >= $cache->getNewest()) {
+      header("HTTP/1.0 304 Not Modified");
+      return false;
+    }
+  }
+
+  foreach($cache->cacheControl() as $header => $value) {
+    header ("${header}: ${value}");
+  }
+  header("Last-Modified: $gmdate_mod");
+  return true;
+}
+
+
+
+/**
+ * CacheTimeCheck provides a set of functions to enable generating a
+ * correct time for the latest update for a given file.
+ *
+ * @author Tom Fredrik Blenning Klaussen
+ */
+class CacheTimeCheck extends FileCacheSet
+{
+  function __construct($filename = False)
+  {
+    parent::__construct();
+    if ($filename)
+      $this->cache_time($filename);
+    $this->cache_time(__FILE__);
+    $this->max_age=0;
+  }
+
+  public function addParent($cache)
+  {
+    parent::addParent($cache);
+  }
+
+  /**
+   * Convenience function to load a file, and add it to the cacheset
+   *
+   * @param $path path of the file
+   * @return the contents of the file
+   */
+  function loadFile($path)
+  {
+    $this->cache_time($path);
+    return loadFile($path);
+  }
+
+}
+?>